ROVERBOX - xlock

simple, cheap and traditional microwave VCO locking

ON4IY and ON4CDU -- January 2007

PCB xlock
prototype  Xlock PCB

0. Xlock?

The Xlock is thought to be a versatile PLL based  frequency stabilisation scheme based up the LMX2306 family of chips (2326 up to 2.8GHz). It uses a PIC16F628(A) microcontroller to load the LMX, and to provide some additional functionality. Why another "reference lock" solution? After having tried all available systems, we felt that price and flexibility still were to be improved. Also the LMX has a nice digital lock detect, to be read and processed by the PIC. Possible applications include microwave LO frequency stabilisation. Also works for ADF4106/4107.


We decided to leave the VCO/RS232 part out - Expanded Spectrum Systems has boards with this setup that work well.
See my Linrad setup.

Latest schematic and PCB and BOM and code

schematic xlockxlock pcb

1. Project status

2. Prototype testing and measurement

XLOCK 1st run
13/02/06 on4iy

Pin Ref 10 dBm

Pin LO 6 dBm

1 2 3 4
Pout thru 8 10.8 10.2 8.5 dBm
Vref LMX 4.5 4.5 4.6 4.5 Vpp
Vlo LMX 1.5 0.9 1.35 1.8 Vpp
Loop filter No – 470K CDU/no 680R CDU/no 680R No – 470K

PIC reads lock, drives external LED to GND

External LED jumper select at startup

3. Todo

Author: Version: Tue Jan 31 14:32:42 MET 2007